Search PubMed⌕ Search

Biomedical subjects

M J Wilson

Publications and source records attributed to M J Wilson.

At least 163 records · Page 9Linked to original sources
PubMed1984

Hypomethylation of DNA in ethionine-fed rats.

Ethionine, the hepatocarcinogenic antimetabolite of methionine, was fed to rats in carcinogenic doses for 1-10 weeks. Levels of 5-methyldeoxycytidine (5-MC) in nuclear DNA and total cellular levels of S-adenosylmethionine (AdoMet) and S-adenosylethionine (AdoEt) were determined at 1, 5 and 10 weeks in livers of control and ethionine-treated animals. The percentage of deoxycytidine residues modified to 5-MC in hepatic DNA of ethionine-fed animals was the same as that in the control animals at 1 week but was 3.6% and 7.6% lower than that observed in control animals at 5 and 10 weeks, respectively. Significant levels of AdoEt, a DNA methylase inhibitor, as well as decreases in the levels of AdoMet were also observed in the livers of ethionine-fed animals. In a second study, the levels of 5-MC, AdoMet and AdoEt were determined in the pancreas, kidneys, testes and thymus of control rats and rats fed ethionine for 10 weeks. Only the testes, an organ known to be susceptible to the toxic effects of ethionine, showed a significant (p less than 0.02) decrease in 5-MC in response to ethionine feeding. AdoEt was present in all tissues studied, except thymus, but at lower levels than those observed in the liver. These results demonstrate that ethionine administration alone under conditions which cause tumors is sufficient for the production of hypomethylated DNA in the target organ and one extrahepatic tissue studied. Hypomethylation of hepatic DNA would appear to result from the accumulation of AdoEt coupled with the decreased levels of AdoMet.

Adenosine↗
PubMed1984

Stereoselective ring oxidation of propranolol in man.

The objective of this study was to elucidate stereoselective mechanisms of propranolol metabolism in man. Five normal subjects were given single 80 mg oral doses of deuterium-labeled pseudoracemates of propranolol, and the stereochemical composition of propranolol and its major metabolites in urine was determined by GC/MS. The (-)/(+)-enantiomer ratios for unchanged propranolol, 1.50 +/- 0.10 (mean +/- s.e. mean), and propranolol glucuronide, 1.76 +/- 0.10, were similar to previous findings in plasma. All products of side-chain oxidation also consisted mainly of the (-)-enantiomer, with an overall (-)/(+) ratio of 1.61 +/- 0.11. A (-)/(+) ratio of 1.04 +/- 0.17 for 4-hydroxypropranolol did not indicate stereoselectivity in ring oxidation. However, the ratio for its glucuronic acid conjugate of 1.78 +/- 0.19 and for its sulphate conjugate of 0.27 +/- 0.03 suggested stereoselectivity in either the glucuronidation or sulphation of 4-hydroxypropranolol, or both. When the stereoselectivity in these secondary pathways was taken into consideration, the overall ring oxidation strongly favoured (+)-propranolol with a (-)/(+)-enantiomer ratio of 0.59 +/- 0.09. The composite observations of the stereochemistry of propranolol metabolism in man are consistent with stereoselective ring oxidation of (+)-propranolol, leading to a greater bioavailability of the pharmacologically more active (-)-propranolol and subsequent preferential side-chain oxidation and glucuronidation of this enantiomer.

Adult↗
PubMed1984

Short-latency auditory responses obtained by cross correlation.

Short-latency auditory responses were derived by cross correlation of pseudorandom white noise with averaged scalp potentials in guinea pigs. The cross-correlation functions were characterized by distinct cochlear microphonic and neural components, as distinguished by susceptibility to hypothermia and masking noise. This technique detects only linear, frequency-following responses of the auditory system, and demonstrated neural frequency following up to 3-4 kHz; thresholds were about 30-40 dB spectrum level. While conventional auditory brain stem responses reflect onset neural activity and are most responsive to high-frequency stimuli, cross-correlation responses reflect frequency-following activity, primarily to low frequencies, and thus may represent a complementary method of electrophysiologic assessment of the auditory system. Data are very rapidly acquired, and estimation of responses of limited areas of the cochlea may be possible by off-line digital filtering of cross-correlation functions obtained with broadband noise stimuli.

Animals↗
PubMed1984

Protein kinase activities in human prostatic secretion: biochemical characterization and effect of prostatitis.

The enzymic properties of two protein phosphokinase activities in human prostatic secretion were determined with partially dephosphorylated phosvitin and lysine-rich histones as acceptor protein substrates. Both kinase activities had pH optima of 8.0 and required Mg2+. The histone kinase activity was stimulated by dithiothreitol and inhibited by increased ionic strength. Similarly, it was inhibited by the cAMP-dependent protein kinase inhibitor. MnCl2 and CaCl2 substituted poorly for MgCl2. In contrast, the phosvitin kinase activity was stimulated by increased ionic strength and inhibited by dithiothreitol. It was, however, unaffected by the cAMP-dependent protein kinase inhibitor. MnCl2 and CaCl2 substituted effectively for MgCl2. Both kinase activities were reduced 60% to 65% in prostatic fluids in men with chronic prostatitis.

Adenosine Triphosphate↗
PubMed1983

Gas chromatographic analysis of chloroquine after a unique reaction with chloroformates.

A specific method for the gas chromatographic determination of chloroquine (CQ) after derivatization with chloroformates, using 9-bromophenanthrene as the internal standard and a column filled with 3% OV-17 on 80-100 mesh Supelcoport is described. Derivatization with chloroformates produced a pyrrolidine derivative, 4-(2-methyl-1-pyrrolidyl)-7-chloroquinoline with CQ, and a carbamate with desethylchloroquine. The chloroformate reaction for CQ is thus selective in the presence of CQ metabolites. The method based on flame ionization detection is highly suitable for quantitation of CQ in urine.

Aminoquinolines↗
PubMed1983

Formation and utilization of methionine by rat liver cells in culture.

The enzyme N5-methyltetrahydrofolate:homocysteine methyltransferase (methionine synthetase) catalyzes the synthesis of methionine from homocysteine. Methylcobalamin is a cofactor for the reaction. The effects of methionine deprivation and methylcobalamin supplementation on the growth of normal and transformed rat liver epithelial cell lines were determined using growth constants to quantitate cell proliferation. No marked specific requirement by the transformed cell lines for methionine relative to leucine was observed. A sigmoidal relationship, however, was found to exist between growth constants and the logarithms of the amino acid concentrations for both normal and transformed cells. Methylcobalamin stimulated the growth rates of the normal and transformed liver cells in methionine-deficient, homocysteine-containing medium. Growth on methionine was not increased by the addition of methylcobalamin. The growth constants for two normal, two spontaneously transformed, one chemically transformed, and one tumor cell line grown in medium in which methionine was replaced by homocysteine were found to be proportional to the level of methionine synthetase. The results demonstrate the utility of growth quantitation to study the methionine dependency of transformed cells.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1983

Tissue sources of protein kinase activities in human seminal fluid: studies of normal, oligozoospermic, and vasectomized men.

Protein kinase activities in seminal fluids of normo-, hypo-, and oligozoospermic and vasectomized men were measured using lysine-rich histones and partially dephosphorylated phosvitin as acceptor substrates. There was a significant relationship of histone kinase but not phosvitin kinase activities with the number of spermatozoa originally present in the semen. Histone kinase and phosvitin kinase activities were diminished 88% and 62%, respectively, in vasectomy seminal fluid. The sex accessory gland sources of seminal fluid protein kinase activities not associated with spermatozoa were examined in split ejaculates of vasectomized men. Histone kinase activity was greater in the first fractions, suggesting that the prostate is its predominant contributor; whereas the distribution of phosvitin kinase activity did not indicate any preferential accessory gland source of this enzyme.

Humans↗
PubMed1983

In vitro assessment of platelet damage during rotator storage.

The measurement of beta-thromboglobulin (BTG) and platelet lactic dehydrogenase (LDH) as markers for alpha-granule release and platelet lysis, respectively, has been reported to correlate with the amount of damage incurred during the preparation and storage of platelet concentrates. We compared the concentrations of these markers in the supernatant plasma of platelets stored on platform, elliptical, and circular rotators. Significant BTG release occurred after 24 hours on all three rotators (P less than 0.01), but LDH discharge after 24 hours was significant (P less than 0.05) only with elliptical rotation. BTG and LDH levels were not significantly different at any time when platform and circular rotations were compared, but both markers were significantly (P less than .05) higher during elliptical rotation. The lower levels of BTG release and LDH discharge during platform and circular agitation implies that these rotators produce less in vitro platelet activation and damage than occurs with elliptical agitation.

Beta-Globulins↗
PubMed1983

Neoplastic conversion of rat liver epithelial cells in culture by ethionine and S-adenosylethionine.

Rat liver epithelial cells were grown in the presence of the hepatocarcinogen, DL-ethionine, for 12 weeks. The cells were then cultured for an additional 32 weeks in carcinogen-free medium. At approximately monthly intervals, the cells were tested for transformation by assaying their ability to grow in soft agar and to produce tumors when injected s.c. into irradiated syngeneic rats. After a total of 34 weeks in culture, cells treated with 7.5 mM DL-ethionine were transformed according to both criteria. The experiment was repeated using medium in which methionine was replaced by its metabolic precursor, homocysteine. The cells were treated for 12 weeks with L-ethionine and its metabolite, S-adenosyl-L-ethionine (L-AdoEt), then cultured in their absence in methionine-containing medium for an additional 24 weeks. After a total of 20 weeks in culture, cells treated with 0.375 mM L-ethionine and cells treated with 0.2 mM L-AdoEt produced tumors following their injection into animals. Positive growth in soft agar was observed 5 and 11 weeks later, respectively. A total of 31 weeks in culture was required before cells treated with 0.2 mM L-ethionine became tumorigenic. Furthermore, tumors resulting from the injection into animals of cells treated with 0.2 mM L-ethionine arose 8-10 weeks later than did the corresponding tumors arising from the cells treated with 0.2 mM L-AdoEt. Thus, the results indicate that AdoEt may be a proximal carcinogenic metabolite of ethionine.

Adenosine↗
PubMed1983

Tissue distribution of methylcobalamin in rats fed amino acid-defined, methyl-deficient diets.

Total cobalamin and methylcobalamin levels were determined in tissues of male F344 rats fed a complete, amino acid-defined diet or a diet deficient in methionine, choline and/or cyanocobalamin. Total cobalamin levels in rats fed the complete diet were (picograms/milligram tissue +/- SEM): liver, 67 +/- 13; kidneys, 738 +/- 133; spleen, 23 +/- 2; and adrenals, 268 +/- 36. Corresponding methylcobalamin levels were: liver, 1.6 +/- 0.5; kidneys, 107.6 +/- 22.2; spleen, 0.3 +/- 0.1; and adrenals, 26.9 +/- 5.3; these values represent 2.4, 14.5, 1.4 and 9.7%, respectively, of the total cobalamin levels. Total cobalamin levels of all tissues studied were altered by cobalamin deprivation alone or in conjunction with methionine and/or choline deprivation. Methylcobalamin levels were more resistant to dietary alteration. Regardless of the presence or absence of methionine and cobalamin in the diet, choline deprivation always decreased the proportion of methylcobalamin in the liver. Kidney levels of methylcobalamin, like those of total cobalamin, were decreased by removal of cobalamin from the complete or the methyl-deficient diets. The results demonstrate that cobalamin, methionine and choline exert quite different effects on tissue levels of the cobalamins in rats.

Adrenal Glands↗
PubMed1983

Inhibition of development of both androgen-dependent and androgen-independent pigment cells in scrotal skin dermis of the rat by antiandrogen treatment during fetal growth.

Testosterone controls the melanogenic activity of epidermal melanocytes, but not that of brown dermal pigment cells, in scrotal skin of the adult rat. The effect of prenatal treatment with the antiandrogen flutamide on the development of scrotal skin pigmentation and the male reproductive system was examined. Treatment with flutamide on days 14-20 of gestation resulted in hypospadias, the absence or only rudimentary growth of prostate and seminal vesicles, and the presence of a vagina in male offspring. The scrotal coloration of these animals was lighter than controls, an effect due to the complete absence of dermal pigment cells. There was no effect of prenatal treatment with flutamide on melanin content, morphology, and relative number of epidermal melanocytes. Thus, the administration of antiandrogen during the fetal period of androgen-induced differentiation of secondary genital organs of the male rat prevents development of the androgen-independent dermal pigment cells. It would appear, therefore, that there is a transitory period during development when the dermal pigment cells or other elements in the scrotal dermal environment which regulate their function are under androgen control.

Androgen Antagonists↗
PubMed1983

Stereoselective increase in propranolol bioavailability during chronic dosing in the dog.

The disposition of (+)- and (-)-propranolol was determined after chronic as compared to single oral doses of racemic drug. Single oral doses (80 mg) of a stable isotope-labeled pseudoracemate were given to six dogs before and after chronic pretreatment with unlabeled propranolol. The bioavailability of (-)-propranolol (5.7 +/- 1.6%; mean +/- S.E.) was considerably lower (P less than .01) than that of (+)-propranolol (16.1 +/- 5.9%) after single doses. Chronic pretreatment led to a 167% increase in the bioavailability of (-)-propranolol to 15.2 +/- 3.7% (P less than .01), with only a 47% increase in (+)-propranolol to 23.7 +/- 4.5% (N.S.). Chronic pretreatment had no effect on the kinetics of i.v. doses of tritium-labeled racemic drug administered simultaneously or on blood binding. This stereoselective increase in the bioavailability of (-)-propranolol was associated with an unexpected 62% increase in the glucuronidation of this enantiomer (P less than .01) with no effect on the glucuronidation of (+)-propranolol. There was, however, a change in the stereochemical composition of 4'-hydroxypropranolol from single doses, (-)/(+)-enantiomer ratio 1.37 +/- 0.14, to chronic doses, 1.23 +/- 0.13 (P less than 0.05), suggesting stereoselective inhibition of ring-oxidation of (-)-propranolol. This study demonstrates preferential presystemic hepatic removal of (-)-propranolol in the dog by a process, probably ring-oxidation, that becomes partially inhibited after chronic doses, leading to a stereoselective increase in the bioavailability of this enantiomer.

Animals↗
PubMed1982

Presence and characterization of two protein kinase activities in human seminal fluid.

The presence of two protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) activities has been demonstrated in human seminal fluid, utilizing partially dephosphorylated phosvitin and lysine-rich histones as model acceptor substrates. Both kinase activities were maximal in the presence of MgCl2 and a sulfhydryl-protecting agent such as dithiothreitol; however, the histone kinase was stimulated to a greater extent by the latter. The histone kinase displayed a broad shoulder of activity at pH values of 7.1 to 7.6 with optimal activity at pH 8.0, and was inhibited by increased ionic strength (53% at 160 mM NaCl) and by the cyclic AMP-dependent protein inhibitor from rabbit muscle. The kinase activity towards phosvitin exhibited a broad pH profile with maximal activity at pH 7.2, was slightly stimulated by NaCl (20% at 160 mM), and was unaffected by the cyclic AMP-dependent protein kinase inhibitor. Kinetic studies revealed more than one apparent Km for the protein substrates and ATP. These differences in enzymic properties of kinase activities towards phosvitin and lysine-rich histones strongly indicate the presence of multiple enzymes. It appears that the histone kinase activity is attributable to the free catalytic subunit of a cyclic AMP-dependent enzyme. The protein kinase activities of seminal fluids from vasectomized men were 12-20% of those found for seminal fluids of normal men. This suggests that sperm may be a major source of protein kinase activities in seminal fluid.

Cations, Monovalent↗
PubMed1982

Phosphoproteins and protein kinase activities of ventral prostate chromatin during sexual maturation in the rat.

1. In the ventral prostates of rats undergoing normal sexual development, chromatin-associated phosphokinase activities toward dephosphophosvitin and lysine-rich histones were maximal at 48 days of age, whereas phosphorylation of endogenous chromosomal proteins was greatest in the sexually mature adult. 2. Polyacrylamide gel electrophoretic analysis of chromatin proteins from these animals revealed age-dependent changes in the amount of phosphorylation of specific proteins. 3. These were most evident in highly phosphorylated H2SO4-soluble nonhistone proteins and in those nonhistones (13-16 K and 20-35 K mol. wt) which are insoluble in H2SO4.

Animals↗
PubMed1981

Nuclear envelope of the seminal-vesicle epithelium.

The nuclear envelope of seminal-vesicle epithelium was isolated by a procedure involving enzymic digestion with deoxyribonuclease I, sonication in the presence of 0.34 M-sodium citrate, and centrifugation through sucrose density gradients. The mass of envelope DNA was only 0.8% of that of envelope protein, and by transmission electron microscopy the envelope was 98-99% pure. We showed that the envelope possess a protein kinase activity which is uninfluenced by cyclic nucleotides. Both lysine-rich histone and dephosphophosvitin as substrates gave a greater specific activity than did envelope protein itself. Optimum requirements with respect to Na+, Mg2+, pH and ATP were established for each substrate, and the influence of other factors on enzyme activity was investigated. Data, obtained mainly with the use of lysine-rich histone, are presented which indicate that nuclear envelope from intact and 96 h-castrated guinea pigs may have equal protein kinase activities and, in separate experiments, equal phosphoprotein phosphatase activities. Clarification of these initial observations must await identification of the natural substrates or the envelope's phosphorylation-dephosphorylation reactions.

Animals↗